FC-14 is used as an etching gas or a cleaning gas in, for example, the manufacturing of semiconductor devices, therefore, a high-purity product thereof is demanded.
For the production of FC-14, various methods have heretofore been proposed. Specifically the following methods, for example, are known:
(1) a method of reacting dichlorodifluoromethane with hydrogen fluoride in the presence of a catalyst;
(2) a method of reacting monochlorotrifluoromethane with hydrogen fluoride in the presence of a catalyst;
(3) a method of reacting trifluoromethane with fluorine gas;
(4) a method of reacting carbon with fluorine gas; and
(5) a method of thermally decomposing tetrafluoroethylene.
However, these methods for producing FC-14 have a problem in that intermediates of FC-14 or by-products produced by the reaction or impurities derived from raw materials form an azeotropic mixture or an azeotrope-like mixture with the objective FC-14 and the separation thereof is extremely difficult. To cope with this, for example, a purification method for treating FC-14 containing trifluoromethane (CHF3), as an impurity, with zeolite or a carbonaceous adsorbent has been proposed (see, Japanese Patent No. 2,924,660).